1. Field of the Invention
The invention relates to the field of ion driven wind or gas generators and in particular to designs capable of operating in mesoscale implementations.
2. Description of the Prior Art
The physics of the ion-driven wind is reasonably well established. When an electric field acts on ions or other charge carriers dispersed in air, the body force on a unit volume of the gas, {right arrow over (F)}, is equal to that on the charges it contains, provided that they have a constant mobility and do not accelerate. Thus{right arrow over (F)}={right arrow over (E)}e(n−+n+)  (1)
and the local current density,{right arrow over (j)}={right arrow over (j)}++{right arrow over (j)}−=(K++n++K−n−){right arrow over (E)}e,  (2)
where {right arrow over (E)}, e, n, K represent electric field, fundamental charge, number density and mobility respectively, and the sign in the suffix denotes the polarity. When the charge cloud is unipolar, or when charge carriers of both polarities are present, but the mobility of one is much greater than that of the other (e.g. electrons and ions, or ions and charged particles) the distribution of body force and consequent pressure gradients results in gas flow. Because of the high potentials generally involved, unipolar clouds are the norm in regions between the relatively small zone of a corona glow ion source and a remote electrode, so long as the field does not reach magnitudes large enough to cause secondary ionization and electrical breakdown of the neutral gas. Thus equation (1) becomes{right arrow over (F)}±={right arrow over (E)}e(n±)  (1a)
and equation (2) becomes{right arrow over (j)}=(K±n±){right arrow over (E)}e  (2a)
so that±{right arrow over (F)}={right arrow over (j)}/K±.  (3)
It follows that, irrespective of the geometry, the body force on the gas and hence the potential to induce velocity is boosted by increasing current density and by decreasing mobility, i.e., utilizing charge carriers which exercise the highest drag on the neutral gas.
The wind generated by ion drag has been termed “corona”, “electric”, “ionic” (chiefly with flames as ion sources), or “electrohydro-dynamically induced”, where the latter term has appeared more recently in application-based studies, i.e. electrostatic precipitation, enhanced drying, and flow control. To emphasize that the gas motion is bulk neutral gas flowing as a result of electric forces acting on ions, the term “ion-driven” wind is used in this disclosure.
Although the first documentation of ion-driven wind occurred in 1709, the first in-depth analysis of the phenomenon was conducted almost 200 years later. There have been numerous studies concerning the use of ion-driven wind velocities for a variety of aerodynamic, heat transfer, and other applications, all of which would benefit from maximizing the gas velocities. Examples include silent mass transfer in low flow (fan-less) electrostatic precipitators U.S. Pat. No. 4,789,801 (1988), flow control, heat transfer, enhanced drying, and combustion control. Much of the work in combustion and some in microgravity were based on using flame ions.